Most airports, especially large airports, currently simultaneously handle large numbers of arriving and departing aircraft of different sizes and body types. The successful management of a large volume of aircraft ground traffic requires careful control of all aircraft ground movement, particularly the movement of departing aircraft. Aircraft parked at a gate or parking area in an airport prior to departure are typically positioned in a perpendicular orientation with the nose of the aircraft facing the gate or airport terminal. Upon departure, the aircraft must move in reverse and make one or more turns before reaching a taxiway prior to taxi and takeoff. Arriving aircraft are moving in a forward direction and turning as required to travel from the runway to a gate or parking location as the departing aircraft are leaving. Departing aircraft must be maneuvered carefully in a reverse direction in an airport ramp area to avoid not only incoming aircraft traveling toward the gates, but also baggage carriers, tugs, and other airport ground vehicles on the trip between the gate and the taxiway.
At the present time, aircraft leaving a gate or other parking location near an airport terminal are pushed in a reverse direction by a tow vehicle or tug that temporarily connects to the aircraft nose landing gear. Once attached to the aircraft, the tug pushes the aircraft in the reverse direction for a distance required to clear the gate to a location where the aircraft is oriented parallel to the terminal and the main engines can be turned on to move the aircraft in a forward direction. The tug is then detached from the aircraft and moved away, and the aircraft is ready to taxi to a runway for takeoff. The movement of tugs and tow vehicles contributes to ground vehicle traffic. Tugs, in addition, must be monitored to keep track of their locations so they may be moved to the next location by the time a tug is needed to push back a departing aircraft. Many aircraft departure delays are the direct result of tug unavailability. This process is time-consuming and may significantly increase the time an aircraft spends on the ground.
Aircraft can also be moved in reverse from a parked position by starting the aircraft's main engines and reversing them to drive the aircraft in a reverse direction. This process, known as reverse thrust, is problematic when used by jet engines and can be dangerous. An aircraft engine operating in reverse thrust may pull foreign object debris (FOD) from the aircraft's environment into the engine and throw it forward, usually in the direction of the gate or airport terminal. The potential for injury to ground personnel, ground vehicles, and airport structures from FOD and also from jet blast from an operating engine can be significant. The use of reverse thrust is prohibited for jet engines and is permitted for use only by turboprop aircraft. Dependence on the use of a departing aircraft's main engines is neither a safe nor an efficient push back procedure.
Airport ground crew are typically assigned to attach and detach tow vehicles and to monitor and direct reversing aircraft to ensure that no part of an aircraft structure will impact any fixed object or other aircraft or vehicle and to communicate with the pilot or another aircraft cockpit crew member. The efficiency and speed with which push back can be conducted depends on the availability of ground personnel as well as the availability of tow vehicles.
The efficiency and speed of aircraft push back operations may be adversely affected by the ground congestion found in most large airports. Multiple airlines conduct both push back and landing operations for multiple aircraft virtually simultaneously. This strains not only the available towing equipment, but also the available ground personnel. Aircraft turnaround times may be increased significantly when tow bars, adapters, tugs, or ground crews are not available for push back when needed. Neither the airline nor the flight crew currently has any control over this situation.
Driving an aircraft on the ground during taxi without reliance on operation of the aircraft's main engines or the use of tow vehicles has been proposed. For example, in commonly owned U.S. Pat. No. 7,469,858 to Edelson; U.S. Pat. No. 7,891,609 to Cox; U.S. Pat. No. 7,975,960 to Cox; U.S. Pat. No. 8,109,463 to Cox et al; and British Patent No. 2457144, aircraft drive systems that use electric drive motors to power aircraft wheels and move an aircraft on the ground without reliance on aircraft main engines or tow vehicles are described. A powered self push back method and system in which aircraft equipped with such drive systems is described in commonly owned International Patent Application Publication No. WO2012109380 A2. This powered self push back method is designed for moving an aircraft parked in a nose-in orientation along a reverse path while turning the aircraft, in the same direction and along the same path as the aircraft would be pushed back with a tug. It is not suggested that an aircraft could travel in reverse along a different path and turn in a different location where the aircraft may taxi forward. Further, it is not suggested that an aircraft could be reversed from a different parking location or orientation other than a nose-in position.
A need exists for a method for powered push back of an aircraft capable of moving independently without reliance on operation of its main engines or tow vehicles that is designed to streamline and accelerate the push back process and reduce aircraft time on the ground.